Understanding Tree Location Importance

Where a tree is planted makes all the difference in terms of its health and ability to flourish.

Ask anyone over 50 years old, “What was the key phrase for good business in the 1970s?” If they can remember correctly, they’d answer “Location, Location, Location,” usually referring to the best place to install a new shopping mall, grocery store or residential subdivision. This reference was basically a real estate term, with location as a first and foremost, primary consideration in any business venture.

But that was then and this is now — or is it?

Actually, in terms of good tree care, location was and remains a primary concern. If there’s any doubt, all that’s necessary to confirm its importance is to run down a list of the components of Integrated Pest Management and Plant Health Care. Of a dozen or so critical factors, location is a crucial and key component. When talking about location, there are many other considerations as well:

Screening trees serve a great purpose in some locations.

Good locations have good soils

Soils that are rich in nutrients, drain freely, resist compaction, hold adequate soil moisture and facilitate structural support are highly desirable for trees. When the spot where a tree is to be planted has these properties, it should be looked upon favorably. Because approximately half of a tree’s growing tissues are below ground, and are dependent on it to perform well in a landscape, healthy soil is a must in terms of a checklist for good locations for trees.

On the other hand, poor soils — ones that are characterized as compacted, nutrient lacking, poorly drained and unstable — are negative factors in consideration of a good location for trees. As with many aspects of arboriculture, Mother Nature provides a model to be replicated in a residential or commercial landscape. In an undisturbed, natural setting, several layers of soil are distinguishable, providing a set of inputs for healthy tree growth. The top layer is the O horizon, otherwise known as “duff,” high in organic matter and nutrients, very well aerated, composed of fallen leaves, twigs, fruits and decaying stems and bark. Under the O horizon is the A, usually lesser in aeration qualities, yet still quite sufficient, dark in color and best described as particles that have an early feel and smell and the consistency of coffee grounds.

As the depth of the soil increases, the quality decreases incrementally. The B layer is characterized by being lesser in terms of fertility and drainage potential, whereas the C horizon is often described as nutrient poor, poorly aerated and inconsistent in drainage qualities. The lowest layer, the R, is often referred to as bedrock, normally devoid of materials that are desirable for tree growth. That’s Mother Nature; in a developed landscape, all bets are off because there may be any combination of these characteristics, either good or bad. A common scenario is that new landscapes contain poor soils because of construction, with C and R horizons being the bulk of the material that tree roots are forced to grow in, while older more mature sites are like those created by Mother Nature. In most situations, tree debris droppage and incorporation has rehabilitated once-disturbed soils into healthy ones that can be counted on to support the needs of trees in the landscape.

Adequate space for roots

In perhaps the simplest of terms, as well as being a quality soil, there must be an adequate amount of soil for a tree to be deemed to be in a good location. While there are no hard and fast rules for soil volume, a few considerations can provide guidance in terms of space for roots.

First, trees differ in terms of need for space. Small ornamentals such as redbud, hawthorn and dogwood don’t require nearly as much as tuliptree and sycamore. Secondly, the depth and nature of rooting should be recognized, such as with silver maple and — species that often express surface rooting characteristics.

The crown projection and lateral spread of the canopy is also a good predictor of required space for rooting. Dr. Nina Bassuk, of Cornell University, recommends that 2.5 cubic feet of soil should be available for every square foot of crown projection of a tree, while Phil Pierce, RCA, suggests that the average medium-sized shade tree ought to have a 1,000-square foot space to grow in. Using these together is a good start toward determining a desirable volume.

Keeping Dr. Bassuk’s and Pierce’s size descriptors in mind, it’s difficult to relate to a common planting site in a downtown or urban location, the hell strip, tree pit or small space next to a street or parking lot. These sites often are only about 25 square feet in size (at best) and are often quite variable in depth. In many cases, trees planted in these spots only live for a few years. Where possible, these locations should be modified with pervious paving and space enlargement to increase tree survival.

Adequate space for rooting leads to the development of healthy roots.

Talking about slopes

Trees located on slopes are put in a difficult growing environment, right from the start. By default, slopes carry with them the limitations of reduced water intake and nutrient retention for trees, and these inputs simply run down the hill, not being held near the roots as would be the case in a flat landscape, or even a slope with a gentle grade change.

As well as the nutrient and water issues, slopes are at odds with maintenance of turfgrass and increase the possibility for physical damage while mowing, aerating or power raking. The potential for damage is inversely related to the age and experience of the maintenance technician, in that older, skilled personnel are much less likely to damage tree trunks and branches than 15-year-olds who just need some quick cash to buy new headphones for their latest electronic device.

Just about any maintenance procedure to reduce the runoff potential on a slope is desirable. Aerating the face to allow for better penetration of rainfall and irrigation water is a good step. Slow, trickle irrigation systems are another. If overhead irrigation is to be used, scheduling the system to operate for several short, 5- to 10-minute cycles is helpful in limiting overspill.

Proper mulching over the basal roots can provide some retention if the mulch is not piled on the trunk.

Small root zone spaces can be improved by enlarging the lateral growth potential and pervious paving.

Harsh site factors

In addition to soil, slope and space, other on-site factors can be limiting in terms of location as well. Reflected glare and sunlight can have a major negative influence on tree growth.

The most common locations where this can be an issue is in office parks and downtown urban corridors, but residential windows can cause damage that may be not fully observed or considered at first. Scorched leaves, peeling bark and leaning are the common symptoms of excessive glare. Salt deposition by street maintenance crews can cause severe injury to tree roots. Unfortunately, this most often occurs in locations where the soils are compacted, which limits flushing of the salts away from the roots, keeping them in contact to cause burning and dieback.

Homeowners sometimes fail to think long term when it comes to tree planting.

The most common outcome is trees that cause damage to foundations, sidewalks, driveways, sprinkler heads and utilities due to their placement. This is bad enough for the homeowner, however, when it occurs between properties to impact neighboring elements, another layer of misfortune is created. A little planning and foresight would have prevented these negative consequences.

Slopes create a special challenge in the landscape.

Right plant, right place

Another consideration of location is the purpose of the tree in the landscape. This is a mutual beneficial relationship between tree and site, with the site providing what the tree needs and the tree providing the desired benefits for the associated people and place.

While there are many purposes of trees in a landscape, four tend to rise to the top. Without question, the provision of shade is universal, in that just about all clients want it and ask for it — while at a garden center picking out a tree, when buying a house and even at cocktail parties when discussing their properties with friends. That magical sweet spot of having enough to moderate high temperatures for outdoor living spaces without needing to rake up copious amounts of leaves in the fall is what most strive for.

Like shade, color is on almost everyone’s mind when it comes to right plant, right place. Spring flowers, summer green leaves and fall red and yellow are the desirable traits for trees in any landscape. In Northern climes, winter features such as bark and fruits offer additional visual benefits.

Screening is another widely-felt need in the landscape, whether to provide a barrier between yourself and a nasty neighbor or to provide visual separation between a property and an ugly municipal site nearby.

Erosion control, fruit production and memorial or historical implications are important as well.